Hemsky came to the Senators in a trade with the Edmonton Oilers at the deadline last season and quickly found chemistry playing on a line with Spezza and fellow winger Milan Michalek. Over his 20 games with Ottawa last year, Hemsky collected four goals and 13 assists.

Now Hemsky and Spezza will be reunited on a Dallas team that already boasted a potent offense, led by center Tyler Seguin and winger Jamie Benn.

Earlier Tuesday, the Senators re-signed Michalek to a three-year deal. That ensured that Ottawa won't lose the entire line that played so well for the team late last year, but the losses of Spezza and Hemsky still represent a big blow.

The pair joins a Stars team earned the final playoff spot in the West last season before falling to the Ducks in the first round in six games.